Hitherto, in general, an electronic watch including analog indication means has hands that are driven by a stepper motor. This stepper motor includes a stator to be magnetized by a coil, and a rotor that is a disc-shaped rotary member magnetized into two poles. For example, the stepper motor is rotationally driven by 180° for each second to indicate the time with the hands.
In such an analog indication-type electronic watch based on a stepper motor, a position indicated by a second hand or the like deviates due to, for example, a backlash of a wheel train configured to move the hands, which causes the second hand or the like to deviate from a dial division. In addition, in order to prioritize miniaturization of the stepper motor, the holding torque of an indicator wheel is reduced, which leads to a problem that, for example, the position of a hand gets out of order due to an impact or the like.
In order to solve such a problem, there is proposed an electronic watch, which is configured so that a drive pulse for driving the stepper motor has a two-step configuration including a first drive pulse and a second drive pulse, and includes a motor control circuit configured to set an output interval between the first drive pulse and the second drive pulse to 50 mS or less (see, for example, Patent Literature 1).
According to the electronic watch of Patent Literature 1, as described therein, it is possible to set the rotation speed of a rotor higher than usual, for example, twice the rotation speed, by outputting the first drive pulse and the second drive pulse having an output interval of 50 mS or less, and hence a speed reduction ratio from the rotor to a second indicator wheel can be increased, to thereby be able to increase the holding torque of the hands and be able to alleviate the deviation of the positions indicated by the hands due to a backlash.
In addition, as a drive method for a stepper motor used in an analog indication-type electronic watch, there is proposed a method involving connecting a first coil and a second coil to a common connection point and switching a current to be applied for each of three phases (see, for example, Patent Literature 2).